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Talking R&P gears without talking about the ratios in the transmission ahead of it is tenuous at best. Running a 3.35 T5 with 3.31 gears is pretty much the same as running a 2.95 T5 with 3.73's in first gear. But you have to consider the rest of the gears too. Also the more power you have, the less gear you can get away with running and the less number of gears you need to do the job. The power seen at the axle is the result of all the gear ratios before it. It's why a 25hp tractor can do so much work.
 

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Talking R&P gears without talking about the ratios in the transmission ahead of it is tenuous at best. Running a 3.35 T5 with 3.31 gears is pretty much the same as running a 2.95 T5 with 3.73's in first gear. But you have to consider the rest of the gears too. Also the more power you have, the less gear you can get away with running and the less number of gears you need to do the job. The power seen at the axle is the result of all the gear ratios before it. It's why a 25hp tractor can do so much work.
I was speaking in generalities and mostly basing it on the days of yore when most of them were still running to the store and the “top dog” had a set of AFR 165’s. You know back when a guy would ask about bolt-ons for his 15 second car and everyone would tell him that spending $800 on parts in labor on a set of 4.10’s was his best bang for buck. $800 spent resulting goring from a 14.7 to a 14.5.
 

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There were two "Astro" companies all along. Astro Transmission Parts makes the A5 gears and was primarily a wholesale business. Astro Performance Warehouse belonged to another family member and went away. Astro Transmission Parts is now doing both wholesale and retail sales. They told me that they do have an order in to have more A-5 gear kits made, but the US Gear manufacturer they use keeps delaying and indicating that the special alloy of steel needed is not available. It has been more than a year since any Astro A5 gears were available, but I believe that more will appear and hopefully it will be later this year... Covid has a play in all of the production issues as well.

Now, the TKX is taking the market by storm! Think of it as a modernized TKO.

The TKX bolts in EXACTLY like the TKO. Internally it is a redesigned TKO with gear ratios that are almost identical, but it shifts better with the multi-cone carbon-fiber synchros. I personally think that for a Fox Mustang the TKX is a better choice, but in some of the older cars the TKX, like the TKO, still has some issues with the fit. Modern Driveline has some videos on how to move the transmission tunnel support and cross member in the early cars to make the TKX fit very nicely.

Stan
 
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'87 Cougah 428W - ⚡Cougar7.0⚡
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Talking R&P gears without talking about the ratios in the transmission ahead of it is tenuous at best. Running a 3.35 T5 with 3.31 gears is pretty much the same as running a 2.95 T5 with 3.73's in first gear. But you have to consider the rest of the gears too. Also the more power you have, the less gear you can get away with running and the less number of gears you need to do the job. The power seen at the axle is the result of all the gear ratios before it. It's why a 25hp tractor can do so much work.
Yep, and there's even more to it than that. I went from 3.73's to 3.55 with the 306 Kenne Bell setup so 1st would be somewhat useful gear again (3.27 1st gear in TKO500.) Now with a large displacement (427.7) N/A combo, it's more complicated. Large displacement adds torque (lower gear), but larger cam affects low-end torque considerably (higher gear.) Larger cam with large single-plane intake & mid-length headers excludes operation below 1400 RPM (higher gear.) Flywheel being lightweight affects drivability (higher gear.) 4th gear finish line RPM (1/4 mile) affects gear desired (3.73 about max.) I stuck with the 3.55's and I can't complain - a decent compromise. My GT500 came with 3.55's from the factory - it's a decent compromise for a typical street oriented car.
 

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The TKX bolts in EXACTLY like the TKO. Internally it is a redesigned TKO with gear ratios that are almost identical, but it shifts better with the multi-cone carbon-fiber synchros.
The TKX is more Magnum 6 speed than it is TKO, which is basically an evolved Top Loader.
 

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The TKX is more Magnum 6 speed than it is TKO, which is basically an evolved Top Loader.
Physically, no, I have to disagree with that. BUT, YES, with the multi-cone synchro technology it does share some great shifting characteristics with the Magnum. Compare the TKO Gear ratios to the TKX. There is barely any difference.

I have the Parts Diagram and the Service Manual for the TKX. When you look at it, it is clearly a TKO inside, but with upgrades and in a new style case.. It even has the same reverse gear mechanism and input bearing retainer.

The Magnum, the TR6060. the T56, and even the T-45 are all from the same family.

Granted, the T-45 was the first generation. It was only a 5-speed and it had issues, but The T-45 uses the very same synchro hubs and rings for gears 1-4 as the original T56.

Stan
 

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Tremec could make any gear ratios they want. I suspect they stuck with what they know the end user wants.
 

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Tremec could make any gear ratios they want. I suspect they stuck with what they know the end user wants.
I think they stuck with that ratio (2.95 1st) in the T5z so they could advertise it at 350 ft lbs of tq vs 300 ft lbs with a 3.35 1st gear. It’s just a conspiracy though.
 

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How easy is it to change the plugs? Ive yet to see P heads in a mustang with easily accessible plugs. It may work but the hassle isnt worth it in my opinion..
With Gt40p specific headers it’s a breeze. With non p long tubes and some 90* boots it can be a real bitch. Not overly time consuming, just takes a little work. I wouldn’t let something tricky that has to be done every 30,000 miles deter you from it.
 
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With Gt40p specific headers it’s a breeze. With non p long tubes and some 90* boots it can be a real bitch. Not overly time consuming, just takes a little work. I wouldn’t let something tricky that has to be done every 30,000 miles deter you from it.
I personally wouldn't ever use them especially with a turbo kit and everything i have gets a turbo or 2. I have 2 sets of 3 bars that i use until i have money to get aluminum heads then the go away till i need them again. I mentioned it because anyone getting into p heads should know it's a pain in the ass to change plugs on P heads with regular headers. It's easier to change plugs in my turbo 95 than p heads with the wrong headers. I've seen people having to make special shortened plug sockets to get them too. My favorite is taking the headers off to get to the plugs cause it's easier lol.
 

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I personally wouldn't ever use them especially with a turbo kit and everything i have gets a turbo or 2. I have 2 sets of 3 bars that i use until i have money to get aluminum heads then the go away till i need them again. I mentioned it because anyone getting into p heads should know it's a pain in the ass to change plugs on P heads with regular headers. It's easier to change plugs in my turbo 95 than p heads with the wrong headers. I've seen people having to make special shortened plug sockets to get them too. My favorite is taking the headers off to get to the plugs cause it's easier lol.
My comment was more geared towards the guy who might just be bolting gt40p’s and aftermarket intake on a car as a weekend project, who might already have a set of long tubes on the car - which I’ve found long tubes to be easier as far as plug boot fitment. Usually a spark plug socket and an offset wrench gets the job done for me.

I’ve done plugs on a turbo car that were an absolute nightmare as well, especially if the wastegate blocks access from the bottom if it’s build by someone who lacks hindsight lol.
 
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I think you mean foresight, but yes. It's mind boggling how many people build or modify cars without thinking about future serviceability.
I think most engineers currently designing cars have this same problem LOL..
 
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I think you mean foresight, but yes. It's mind boggling how many people build or modify cars without thinking about future serviceability.
Ahh yes foresight
 

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65 fastback pump gas .060 289 (297) solid roller, T5 all motor. 11.12 122 mph
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[

I went from 3.73’s to 3.31 & I’m never looking back. The “don’t fear the gear” guys always over-sell the performance difference between say a 3.08 and the 4.10’s on a street car. We’re talking “split seconds,” like hundredths at best. At the drag strip a millisecond might make or break someone but not in the real world.
First off what is your 60ft at the track big mouth? Have you ever put slicks on your car and launched wide open throttle off the two step? You have not a clue what you are talking about. Torque at the tire for the win. That’s me lioftimg a cotton ball for you to connect with.
 
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